A zoom camera, whether it is a film type camera or a digital camera, generally includes a zoom lens barrel assembly having a zooming function for varying magnification (i.e., a focal length) of a photographing lens and a focusing function for varying a focal point in response to the distance to a subject.
The zoom lens barrel includes front and rear lens barrel assemblies. The rear lens barrel assembly includes a lens whose focal length may be slightly deviated from the optimal by a production tolerance. In order to adjust the deviated focal length, a plate having a predetermined thickness is inserted between the lens barrel and a film or between the lens barrel and a charging surface of a charge coupled device (CCD) in the course of assembling the lens to the lens barrel. Alternatively, a screw or a cam may be used to adjust the focal length.
The above-described adjusting methods have an advantage of accurately adjusting the focus at a central portion of the lens. However, there is still a problem that the focus at a periphery of the lens (i.e., a resolution power) may be varied due to the production and assembling tolerances, thus deteriorating a resolution power of the lens or the zoom camera. In this disclosure, adjusting of the focus means an adjustment or correction activity to make a lens barrel or a whole camera incorporating such a lens barrel to be in focus with respect to an infinity subject.
In order to adjust the focus and the resolution power at the periphery of the lens, the barrel should be disassembled, or the barrel should be rotated and reassembled, or the lens should be replaced with a new one, after which a test should be performed again. This may cause the increase of the working time, deteriorating the productivity.